Osmotic devices for delivering a beneficial agent to environments of use are known to the prior art in U.S. Pat. No. 3,845,770 issued to Theeuwes and Higuchi, and in U.S. Pat. No. 3,916,899 issued to the same patentees. The osmotic devices disclosed in these patents comprise a semipermeable wall that surrounds a compartment containing a beneficial agent. The semipermeable wall is permeable to the passage of an external fluid, and it is substantially impermeable to the passage of agents. A passageway is provided through the wall for delivering the beneficial agent from the device. These prior art devices release the beneficial agent by imbibing fluid through the semipermeable wall into the compartment in a tendency towards osmotic equilibrium, at a rate determined by the permeability of the wall and the osmotic pressure gradient across the wall, to form in the device an aqueous solution containing the beneficial agent that is dispensed through the passageway from the device. These devices are extraordinarly effective for delivering an agent that is soluble in the fluid and exhibits an osmotic pressure gradient across the semipermeable wall against the external fluid, and for delivering an agent that has limited solubility in the fluid and is admixed with an osmotically effective compound that is soluble in the fluid and exhibits an osmotic pressure gradient across the semipermeable wall against the fluid. The beneficial agent is incorporated into these devices during manufacture, prior to forming the semipermeable wall around the compartment.
The prior art devices operate successfully for delivering a wide variety of aqueous-soluble beneficial agents to an environment of use. The devices also are successful for delivering numerous difficult to deliver agents to an environment of use. Prior to this invention, as noted immediately above, the devices were filled with a beneficial agent at the time of manufacture. Now it has been discovered the use of these devices can be enhanced by providing a device that can be filled with the agent at the time of use. For beneficial agents that are sensitive to fluids and light, and for agents that are subject to degradation and possess a short shelf life and, therefore, do not readily lend themselves to previous manufacture, this invention provides a device that can be filled with an agent at the time of use. The devices of this invention can be filled by the hospital pharmacists, the nurse, the physician, or by the veterinarian at the time of use and need for dispensing the beneficial agent to the recipient.